1. Field of the Invention
The present invention relates to a pulse light source and a pulse compression method.
2. Related Background Art
A pulse light source is used for industrial applications represented by machining and the like, and has a trend that a higher power output and a shorter pulse width are desired. In particular, the pulse light source used in a laser beam machine for micro-machining is desired to have a higher peak value and also a narrower pulse width for reducing a heat effect to an object to be machined as much as possible.
A Q switch, a mode lock, or the like has been proposed as a structure for generating pulse light in a gas laser light source or a solid laser light source (see Non-patent document 1). Further, a gain switching method using a semiconductor laser also attracts attention as a simpler method. The gain switching is realized after all by direct modulation of the semiconductor laser, and thereby, a pulse repetition rate thereof is not restricted by a hard structure as in the mode lock and does not need an expensive component such as an acousto-optic switch, which consumes huge electric power, as in the Q switch.
However, the semiconductor laser has a low optical output power in general compared to conventional laser light sources such as the gas laser light source and the solid laser light source, and is used generally for communication or measurement. Therefore, the semiconductor laser has not been required to have a high pulse peak power (see Non-patent documents 1 and 2).    Non-patent document 1: Cho-kosoku hikari gijutsu (Ultra high speed light technology), 2nd part, published by Maruzen in March 15, in 1990.    Non-patent document 2: M Kakui, et al., Optical Fiber Technology, vol. 1, pp. 312-317, 1995.    Non-patent document 3: F. D. Teodoro, et al., PhotonicWest 2005.    Non-patent document 4: J. Limpert et al., Optics Express, vol. 11, p. 3332, 2003.